Mononuclear copper(II) complexes with 3,5-substituted-4-salicylidene-amino-3,5-dimethyl-1,2,4-triazole: synthesis, structure and potent inhibition of protein tyrosine phosphatases

Synthesis, Spectral, Thermal and Biological Studies of 4-Cyclohexyl-3-(4-nitrophenyl)methyl-1,2,4-triazolin-5-thione and Its Copper(II) Coordination Compound, [CuCl2(H2O)2L2]

One of the strategies for seeking new biologically active substances is to modify compounds with potential biological activity. In this paper, 1,2,4-triazolin-5-thione derivative (3) was obtained in the cyclization reaction of appropriate thiosemicarbazide (2) as an organic ligand. The copper(II) complex, [CuCl2(H2O)2L2] (L=4-cyclohexyl-3-(nitrophenyl)methyl-1,2,4-triazolin-5-thione) (Cu-3) was prepared in a reaction of free ligand (3) with a CuCl2·2H2O solution in MeOH/EtOH mixture at room temperature. TGA data show that Cu-3 and free ligand are stable at room temperature. Both compounds were screened in vitro for antibacterial and antifungal activities using the broth microdilution method. The obtained complex (Cu-3) showed higher antibacterial effect, especially towards Gram-positive bacteria (with moderate activity and Minimal Inhibitory Concentration MIC = 250-500 µg/mL) than the free ligand (3) (with mild or no bioactivity and MIC ≥ 1000 µg/mL). In turn, yeasts, belonging to Candida albicans, exhibited similar sensitivity to both the copper(II) complex (Cu-3) and the organic ligand (3). The anticandidal activity of these compounds was moderate (MIC = 500 µg/mL), or, in the case of other Candida spp., lower (MIC ≥ 1000 µg/mL).

Design and Biological Evaluation of Novel Imidazolyl Flavonoids as Potent and Selective Protein Tyrosine Phosphatase Inhibitors

BACKGROUND

Protein tyrosine phosphatases 1B are considered to be a desirable validated target for therapeutic development of type II diabetes and obesity.

METHODS

A new series of imidazolyl flavonoids as potential protein tyrosine phosphatase inhibitors were synthesized and evaluated.

RESULTS

Bioactive results indicated that some synthesized compounds exhibited potent protein phosphatase 1B (PTP1B) inhibitory activities at the micromolar range. Especially, compound 8b showed the best inhibitory activity (IC50=1.0 µM) with 15-fold selectivity for PTP1B over the closely related T-cell protein tyrosine phosphatase (TCPTP). Cell viability assays indicated that 8b is cell permeable with lower cytotoxicity. Molecular modeling and dynamics studies revealed the reason for selectivity of PTP1B over TCPTP. Quantum chemical studies were carried out on these compounds to understand the structural features essential for activity.

CONCLUSION

Compound 8b should be a potential selective PTP1B inhibitor.

Identification of novel imidazole flavonoids as potent and selective inhibitors of protein tyrosine phosphatase

A series of imidazole flavonoids as new type of protein tyrosine phosphatase inhibitors were synthesized and characterized. Most of them gave potent protein phosphatase 1B (PTP1B) inhibitory activities. Especially, compound 11a could effectively inhibit PTP1B with an IC₅₀ value of 0.63 μM accompanied with high selectivity ratio (9.5-fold) over T-cell protein tyrosine phosphatase (TCPTP). This compound is cell permeable with relatively low cytotoxicity. The high binding affinity and selectivity was disclosed by molecular modeling and dynamics studies. The structural features essential for activity were confirmed by quantum chemical studies.

Crystal structure of tetrakis(μ2-acetato-κ2 O:O′)-bis[μ3-4-chloro-2,6-bis((methylimino)methyl)phenolato-κ2 N,O:O,N′]-(μ4-oxido)tetracopper(II), C28H32Cl2Cu4N4O11

C28H32Cl2Cu4N4O11, triclinic, P1̅ (no. 2), a = 9.115(3) Å, b = 12.769(4) Å, c = 14.870(5) Å, α = 93.796(5)°, β = 93.548(5)°, γ = 91.917(5)°, V = 1722.2(10) Å3, Z = 2, R gt(F) = 0.0303, ω Rref(F2) = 0.082, T = 298 K.

A dioxidovanadium (V) complex of NNO-donor Schiff base as a selective inhibitor of protein tyrosine phosphatase 1B: Synthesis, characterization, and biological activities

A new dioxidovanadium (V) complex, VO₂(HPPCH) (1) (H₂PPCH = N'-picolinoylpyridin-1-ium-2-carbohydrazonate) has been synthesized and characterized by elemental analysis, IR, X-ray diffraction analysis and electrospray ionization mass spectra. Complex 1 crystallized in the monoclinic system with space group P2₁/c. It potently inhibited PTP1B with IC₅₀ of 0.13 μM, about 7, 15 and 125-fold stronger against PTP1B than over TCPTP, SHP-1 and SHP-2, displaying obvious selectivity against PTP1B. Western blotting analysis indicated that complex 1 effectively increased the phosphorylation of PTP1B substrates, especially the phosphorylation of IR/IGF 1R and IRS-1. It exhibited lower cytotoxicity than positive control VOSO₄. These results make complex 1 a promising candidate for novel anti-diabetic drug development.

The metal face of protein tyrosine phosphatase 1B

A new paradigm in metallobiochemistry describes the activation of inactive metalloenzymes by metal ion removal. Protein tyrosine phosphatases (PTPs) do not seem to require a metal ion for enzymatic activity. However, both metal cations and metal anions modulate their enzymatic activity. One binding site is the phosphate binding site at the catalytic cysteine residue. Oxyanions with structural similarity to phosphate, such as vanadate, inhibit the enzyme with nanomolar to micromolar affinities. In addition, zinc ions (Zn2+) inhibit with picomolar to nanomolar affinities. We mapped the cation binding site close to the anion binding site and established a specific mechanism of inhibition occurring only in the closed conformation of the enzyme when the catalytic cysteine is phosphorylated and the catalytic aspartate moves into the active site. We discuss this dual inhibition by anions and cations here for PTP1B, the most thoroughly investigated protein tyrosine phosphatase. The significance of the inhibition in phosphorylation signaling is becoming apparent only from the functions of PTP1B in the biological context of metal cations as cellular signaling ions. Zinc ion signals complement redox signals but provide a different type of control and longer lasting inhibition on a biological time scale owing to the specificity and affinity of zinc ions for coordination environments. Inhibitor design for PTP1B and other PTPs is a major area of research activity and interest owing to their prominent roles in metabolic regulation in health and disease, in particular cancer and diabetes. Our results explain the apparent dichotomy of both cations (Zn2+) and oxyanions such as vanadate inhibiting PTP1B and having insulin-enhancing ("anti-diabetic") effects and suggest different approaches, namely targeting PTPs in the cell by affecting their physiological modulators and considering a metallodrug approach that builds on the knowledge of the insulin-enhancing effects of both zinc and vanadium compounds.

A Study on the Condensation Reaction of 4-Amino-3,5-dimethyl-1,2,4-triazole with Benzaldehydes: Structure and Spectroscopic Properties of Some New Stable Hemiaminals

Studies on the stable hemiaminals and Schiff bases formation in the reaction of substituted benzaldehydes with primary 3,5-dimethyl-1,2,4-triazole 4-amine were carried out under neutral conditions. These products were investigated by IR, Raman, MS, ¹H- and ¹³C-NMR spectra as well as by X-ray crystallography. The effect of reaction conditions: temperature, polarity of the solvents utilized, substrate concentration and the ortho and para benzaldehyde substituents on the yield of products was also examined.

Protein tyrosine phosphatase inhibition by metals and metal complexes

SIGNIFICANCE

Protein tyrosine phosphatases (PTPs) play essential roles in controlling cell proliferation, differentiation, communication, and adhesion. The dysregulated activities of PTPs are involved in the pathogenesis of a number of human diseases such as cancer, diabetes, and autoimmune diseases.

RECENT ADVANCES

Many PTPs have emerged as potential new targets for novel drug discovery. PTP inhibitors have attracted much attention. Many PTP inhibitors have been developed. Some of them have been proven to be efficient in lowering blood glucose levels in vivo or inhibiting tumor xenograft growth.

CRITICAL ISSUES

Some metal ions and metal complexes potently inhibit PTPs. The metal atoms within metal complexes play an important role in PTP binding, while ligand structures influence the inhibitory potency and selectivity. Some metal complexes can penetrate the cell membrane and selectively bind to their targeting PTPs, enhancing the phosphorylation of the related substrates and influencing cellular metabolism. PTP inhibition is potentially involved in the pathophysiological and toxicological processes of metals and some PTPs may be cellular targets of certain metal-based therapeutic agents.

FUTURE DIRECTIONS

Investigating the structural basis of the interactions between metal complexes and PTPs would facilitate a comprehensive understanding of the structure-activity relationship and accelerate the development of promising metal-based drugs targeting specific PTPs.

2-[(E)-(4-Bromo-phenyl)imino-methyl]-4-chloro-phenol

In the title compound, C13H9BrClNO, the dihedral angle between the substituted benzene rings is 44.25 (11)°. There are strong intra-molecular O-H⋯N hydrogen bonds, which generate S(6) rings, and also inter-molecular Cl⋯Cl [3.431 (3) Å] and Br⋯ Br [3.846 (1) Å] contacts. The crystal packing a C-H⋯O and C-H⋯π inter-actions.

4-[(5-Bromo-2-hy-droxy-benzyl-idene)amino]-3-propyl-1H-1,2,4-triazole-5(4H)-thione

The asymmetric unit of the title compound, C₁₂H₁₃BrN₄OS, contains two independent mol­ecules in which the dihedral angles between the triazole and benzene rings are 2.9 (3) and 7.5 (3)°. The thione group is of the form R₂C=S. An intra­molecular O—H⋯N hydrogen bond occurs in each mol­ecule. The crystal structure features weak N—H⋯S inter­actions and π–π stacking of the benzene rings [centroid–centroid distance = 3.667 (3) Å].

Exploration of biguanido-oxovanadium complexes as potent and selective inhibitors of protein tyrosine phosphatases

The inhibitory effects of three biguanido-oxovanadium complexes ([VO(L(1-3))(2)]·nH(2)O: HL(1) = metformin, HL(2) = phenformin, HL(3) = moroxydine) against four protein tyrosine phosphatases (PTPs) and an alkaline phosphatase (ALP) were investigated. The complexes display strong inhibition against PTP1B and TCPTP (IC(50), 80-160 nM), a bit weaker inhibition against HePTP (IC(50), 190-410 nM) and SHP-1(IC(50), 0.8-3.3 μM) and much weaker inhibition against ALP (IC(50), 17-35 μM). Complex 3 is about twofold less potent against PTP1B, TCPTP and HePTP than complexes 1 and 2, while complex 2 inhibits SHP-1 more strongly (about three to fourfold) than the other two complexes. These results suggest that the structures of the ligands slightly influence the potency and selectivity against PTPs. The complexes inhibit PTP1B and ALP with a typical competitive type.

Potent inhibition of protein tyrosine phosphatases by quinquedentate binuclear copper complexes: synthesis, characterization and biological activities

Three phosphono-containing multidentate ligands were employed to synthesize quinquedentate binuclear copper complexes, [Cu(2)L(2)] (1-3) (H(2)L1 = diethyl(propane-1,3-diylbis(azanediyl))bis((2-hydroxyphenyl)methylene)bis(hydrogen phosphonate), H(2)L2 = diethyl(ethane-1,2-diylbis(azanediyl))bis((2-hydroxyphenyl)methylene)bis(hydrogen phosphonate), H(2)L3 = diethyl(hexane-1,6-diylbis(azanediyl))bis((2-hydroxyphenyl)methylene)bis(hydrogen phosphonate)), which were characterized by elemental analysis, IR, X-ray diffraction analysis, electrospray ionization mass spectra. Complexes 1 and 2 crystallized in the triclinic system with space group P ̅1. The speciation of the Cu-H(2)L1 system in aqueous solution was investigated by potentiometric pH titrations. The three dicopper complexes exhibited potent and almost the same inhibitory effects against protein tyrosine phosphatase 1B (PTP1B) and T-cell protein tyrosine phosphatase (TCPTP) with IC(50) of 0.16-0.24 μM, about 10-fold stronger inhibition than against Src homology phosphatase 1 (SHP-1), 30-fold than against Src homology phosphatase 2 (SHP-2) and more than 100-fold than against megakaryocyte protein-tyrosine phosphatase 2 (PTP-MEG2). Fluorescence titrations revealed complex 1 bond to the five PTPs with molar ratio of 1:1 and binding constants of 1.62 × 10(6), 3.09 × 10(6), 1.95 × 10(5), 2.24 × 10(5), 1.55 × 10(4) M(-1) for PTP1B, TCPTP, SHP-1, SHP-2 and PTP-MEG2, respectively, consistent with the inhibitory abilities from IC(50) and K(i) values. Also, the three copper complexes could inhibit phosphatase activity of cell extracts from C6 rat glioma cells. The results suggested the structures of copper complexes influence selectivity over different PTPs.

Dinuclear copper complexes of organic claw: potent inhibition of protein tyrosine phosphatases

Three dinuclear copper complexes of organic claw ligands (2,2',2″,2'''-(5-R-2-hydroxy-1,3-phenylene)bis(methylene)bis(azanetriyl)tetraacetic acid, R=methyl (H(5)L1), chloro (H(5)L2) and bromo (H(5)L3)): [Cu(2)NaL1(H(2)O)(2)] (1), [Cu(2)HL2(H(2)O)(2)] (2), [Cu(2)NaL3(H(2)O)(2)] (3), have been synthesized and characterized by elemental analyses, infrared spectra, thermo-gravimetric analyses, X-ray diffraction analysis, electrospray ionization mass spectra, pH-potentiometric titration, molar conductivity. Their inhibitory effects against human protein tyrosine phosphatase 1B (PTP1B), T cell protein tyrosine phosphatase (TCPTP), Megakaryocyte protein tyrosinephosphatase 2 (PTP-MEG2), srchomology phosphatase 1 (SHP-1) and srchomology phosphatase 2 (SHP-2) are evaluated in vitro. The three copper complexes exhibit potent and almost same inhibition against PTP1B and SHP-1 with IC(50) values ranging from 0.15 to 0.31μM, about 2-fold stronger inhibition than against PTP-MEG2, 10-fold stronger inhibition than against TCPTP, but almost no inhibition against SHP-2. Kinetic analysis indicates that they are reversible competitive inhibitors of PTP1B. Molecular docking analyses confirm the inhibition model. Fluorescence titration studies suggest that the complexes bond to PTP1B with the formation of a 1:1 complex. The results demonstrate that copper complexes that are potent PTPs inhibitors but have different inhibitory effects over different PTPs, may be explored as new practical inhibitors towards individual PTP with some specificity.

Potent inhibition of protein tyrosine phosphatases by copper complexes with multi-benzimidazole derivatives

A series of copper complexes with multi-benzimidazole derivatives, including mono- and di-nuclear, were synthesized and characterized by Fourier transform IR spectroscopy, UV-Vis spectroscopy, elemental analysis, electrospray ionization mass spectrometry. The speciation of Cu/NTB in aqueous solution was investigated by potentiometric pH titrations. Their inhibitory effects against human protein tyrosine phosphatase 1B (PTP1B), T-cell protein tyrosine phosphatase (TCPTP), megakaryocyte protein tyrosine phosphatase 2 (PTP-MEG2), srchomology phosphatase 1 (SHP-1) and srchomology phosphatase 2 (SHP-2) were evaluated in vitro. The five copper complexes exhibit potent inhibition against PTP1B, TCPTP and PTP-MEG2 with almost same inhibitory effects with IC(50) at submicro molar level and about tenfold weaker inhibition versus SHP-1, but almost no inhibition against SHP-2. Kinetic analysis indicates that they are reversible competitive inhibitors of PTP1B. Fluorescence study on the interaction between PTP1B and complex 2 or 4 suggests that the complexes bind to PTP1B with the formation of a 1:1 complex. The binding constant are about 1.14 × 10(6) and 1.87 × 10(6) M(-1) at 310 K for 2 and 4, respectively.